Process for forming urea complexes



Patented Nov. 10, 1953 PRocEssioRroRM'ING UREA ooMPI'LExEs. George B.- Arnold; Glenham, and James K. Timm and Howard V. Hess, Beacon,V

to The Texas Company,

poration ofDelaware N. Y., assignors NewYork, N. Y., arcuri No Drawing. Application February 11, 1950,

' Serial No. 143,838

This.. invention relates` toA the formation of Y urea complexes by contact of an organic mixture with urea in a medium which possesseslow hydrocarbon solubilities. More particularly, this invention discloses amethod for catalyzing the formation of urea complexeswhen the complexingagent is used in an aqueous solution or slurry.

This invention involves the discovery that formation of urea-hydrocarbon complexes by contact of a mixtureof `organic compounds with urea in a medium such as Water which possesses a low hydrocarbon solubility, isfacilitated by the presence lof addedjcomplex.v The presence of addedcomplexduringcontact of an organic mix,- ture with urea-actsias apromoter for the formation of complex. Advantageous1y, the added complex contains organic constituents similar in compositiongto those present in VtheY mixture to be treated. The simplestmethod of maintaining a constant. quantityjof complex in the contacting zone consists of recycling a portion` ofthe complex. The process of the. invention is particularly'- useful when `Water isemployed as the urea medium;

It has recently been discovered that urea forms a solid complex With certainv types of organic compounds. The class of compounds which complex-with urea comprises Anormal aliphatic hydrocarbons containing at least six carbon atoms, terminal-substituted normal aliphatic hydrocarbons containing'oat least six carbon atoms,`

suchv as n-decanol` and VnV-dodecylbenzene and someI` methyl-substituted `n-aliphatic hydrocar bons. This discovery provides; a very useful tool inAv the resolutionv of lorganic mixtures, vsuch as petroleum'ffractions andthe oil product obtained by catalytic conversion of carbon monoxide and hydrogen. Urea complexing is useful both in the isolation of specific compounds, and .inthe removal of undesirable components from'a petro.

leum fraction. The main commercial usefulnessVv of urea complexing at the present .time lies 'the deWaXIlg 0f petroleum-fractions such as gas oil and lubricating oils, to produce low pour products.l Low pour-diesel-l fuels -are-in -demand as,.jet.,fuelsv and for.- cold Weather operation of diesel engines;` refrigerator oils lcharacterized by 1oW..Fr.eon haze .are required in air-conditioning andrefrigeration equipment. f f

Various procedures Ahave been proposed for ef` 50" fecting formation of--ureacomplexes Withorg'anicf compounds. It has been proposed thatpcomplex Vformationgbe effected by-contacting lanorganic L mixture 4with :a saturated; 6rsupersaturatedv solue tiozzuofA urea-finla polar solvent;y -suchasA aliphatic 4 claims. (ci. 26o-46.5)

24 alcohols, aliphatic ketonesgwater, etc. ComplexE formation is also effected by contacting an or-Y ganic mixture with a slurry of urea in a polarsol-`V vent. Complex formation is also effected by con-" tacting an organic mixturejwith a fixed bed of urea; in procedures'of this sort thej'ur'ea is ad vantageously used in conjunction with apart-.icmV late solid, such as 4Filter' Cel, alumina, silica, sand, etc. In all these various techniques Afor effecting complex formation the presence 'of a polar compound, such as fwater, an a1iphatical-- cohol or an aliphatic ketone'expeditesicomplex" formation.

TheV discovery that urea complex formation can',v be effected by contact of an organic mixturejw'ith an aqueous solution Aor'slurrygof 'ureah'asresulted in substantial economies" in the applica-'i V tion ofurea complexing to commercial'operations'." Since aqueous solutionis'readily separated from the organic mixture, and` sinceresidual 'Waten" is simply removed from 'the' organic mixture;

contamination of organic mixture, suChaS" de"v waxed gas oil is obviated. The aqueous'solution: employed for urea complexing should'be subl stantially `saturated ,and isV preferably supersaturated or an aqueous 'slurry of urea." Dilute aqueous solutions are'r'ietjfeflective"for complex t formation becausethe complexj isdecomposed 'by'i the extra-'dissolvingA power `Vofja 'diluted aqueous* urea solution. f The process of this inventionV is" particularly useful when Wateris'employed as theure'asolf.. vent. However, thepresence"of added compiex during contact of urea With'tlieorganic mixture results `in Ymore completeand rapid coinplexfforl' mationfwhen other'urea mediums which possess j a lowhydrocarbon solubility vare used." 'lhus;"' theY invention is useful vvh'enlow molecular weight In accordance with the 'process ofjthis inve tion,` complex formation a` medium whichy possesses lowhydrocarbonfsolubility is"subst`an`" tiallyenhancedfbythe presenceV of added" com plex. I-Iereafter,Av the invention Willbe'` illustrated"" by 'complexrformation byA contact with urea in"v aqueous medium.V The improvement isparticuji larly noticeable when `the organic mixture, which is subjected;` to4 complex formation, comprises heavier Aoil stocks', suchyas lubricating oil fra'of Y, tions.V vFor example, inthedewaxing of 'lubricating oil fraction With'an aqueous slurry of ur y' a Freon liazejof -`F. 'Was'obtained Withco `plex recycle,` whereas the basti products., obtain plex recycle had a Freon haze of -20 F. Substantial improvement is also realized in the formation of complexes with lighter molecular weight oils, such as gas oils, although the improvement in such instances is not as striking as when the charge stock is a heavier oil. The presence of complex during contacting of the charge material with urea in aqueous medium results in more complete and rapid reaction between urea and complex-forming compounds present in the mixture.

The most practicable procedure for effecting complex formation with urea in the presence of added complex involves recycle of separated complex to the zone wherein the organic mixture is contacted with urea. During initial contact of aqueous urea with the organic mixture, complex from an extraneous source can be added to promote complex formation. An alternative starting up procedure involves recycle of products during the period of initial contact.

rAlthough recycle of complex is the preferred procedure for eecting complex formation in the presence of added complex, the invention also contemplates addition of complex from an external source. Added complex from an external source can be composed of urea and a straight chainv aliphatic hydrocarbon containing at least six carbon atoms'or a terminally-substituted normal aliphatic hydrocarbon containing at least six carbon atoms. Advantageously, the organic component of a complex added from an external source is of similar composition to the complexforming materials in the organic mixture to be treated.

When complex recycle is employed to provide the presence of added complex during the formation of complex by contacting an organic mixture with urea in .aqueous medium, it has been Vdiscovered that excellent results are obtained with complexrecycle in the amount of 5 to 40 pounds of recycle per barrel of oil treated. A recycle ratio of about to 30 pounds of complex per barrel of oil VtreatedV is particularly eiective.

Normal methods of complex formation and complex separati-cn are employed in the process of this invention. It is preferred to use slurry of urea although saturated and super-saturated aqueous solutions may also be employed. Advantageously, vigorous agitation is used to eiect good contact of urea with the organic mixture.

The process of this invention is particularly effective when solubilizing solvents are employed in conjunction with complex recycle in the fory mationV of urea complexes. Y The dewaxing of enhanced Whencomplex recycle is employed in conjunction with the use of solvents which en- Y hance the miscibility of the aqueous phase with Solvents which increasethe organic mixture. the miscibility of the tvvov phases are. ketones, such as acetone, methyl ethyl ketone and methyl effected at temperatures between 0 and 150V F. and preferably at temperatures between 70 and lubricating oils and gas oil by aqueous urea is .isobutyl ketone, alcohols, such as ethanol, butanol l 140 F., thereby eliminating the necessity of refrigeration. Atmospheric temperature has been found to be a convenient, eirective temperature at which to contact urea with a mixture of organic compounds. Apparently, complex formation is not critical to pressure so that pressures ranging from subatmospheric to super-atmospheric pressures up to and above 20 atmospheres may be employed. However, complex formation is ordinarily effected at atmospheric pressure. Y Separation of the complex from the organic mixture is eiected by filtration, centrifugal separation or settlers. Rotary filters, such as are employedk in solvent dewaxing, are useful in effecting continuous filtration of complex from reaction mixture. Centrifugal separation has also proven very useful in the removal of complex in continuous operation. Settlers are used in batch operation. The process of the present invention is accompanied by substantial improvements no matter what method of contacting or separation procedure is employed.

The accompanying examples illustrate the advantages realized in the process of this invention.

In Examples I to IV, there is shown the eiiect of dewaxing of turbine oil with and without complex recycle; Examples V and VI illustrate dewaxing of gas oils with aqueous urea with and Without complex recycle.

Example I A turbine oil, whose Freon haze was above 20 F. was contacted in a reaction vessel with an aqueous slurry of urea in theA proportion of one volume of slurry per ten volumes of oil. The

ture was maintained between about 71 and 74 F.

in the reaction vessel and the total contact time was 1%/ hours. of complex had a Freon haze of 60 F.

Example II A turbine oil whose Freon haze was above 20 F. was contacted in a reaction vessel withV an aqueous slurryrof urea in the proportion of one volume of slurry per 10 volumes of oil. The

aqueous slurry contained 35 pounds of urea per barrel oi oil over and above the urea required to saturate the aqueous solution at about F.,l

Separated complex kwas recycled to the reaction vessel in the proportion of about 28 pounds of complex per barrel'of oil treated. The temperature was maintained between about 82 and 84Vo F, in the reaction Vessel. The stirring htime was one half hourl and the total contact time was onehour. The Aiiltrate Yoiiaiter separation from.

complex' has a Ereon haze of 55 F.

Efclample III A turbine oil whose Freon haze was above-'20 F. Was contacted in a reaction Vessel with aslurry of urea in the proportion of one Volume of slurry perl() volumes ofoil. The'aqueous slurry contained 35 pounds of urea per barrel of oil' over and above the urea required to saturate the aqueous solution at about 80 F. The separated complexv was recycled to the reaction vessel in the proportion of about 28 pounds of complex per barrel of oil treated.V `The temperature was maintained between about@ and 84? E, in the, reaction:

The nitrate oil after separa-tion vessel and the total contact time was two hours; total stirring time was one hour. The iiltrate oil after separation of, complex has a Freon haze of 65 F.

Example IV A turbine oil Whose Freon haze Was above 20 F. was contacted in a reaction vessel with an aqueous slurry of urea in the proportion of one volume of slurry per two volumes of oil. The aqueous slurry contained 29 pounds of urea per barrel of oil over and above the urea required to saturate the aqueous solution at about 80 F. There was no complex recycle in this example. The temperature Was maintained at about 82 and 84 F. in the reaction vessel and the total contact time Was 171/2 hours; total stirring time was one hour. The iiltrate oil after separation of complex had a Freon haze above 20 F.

Example V .A gas oil which had a pour point of 25 F. was contacted in a reaction vessel with an aqueous slurry of urea in the proportion of one volume of slurry to volumes of oil. The aqueous slurry contained 140 pounds of urea per barrel of oil over and above the urea required to saturate the aqueous solution at about 80 F. The separated complex was recycled to the reaction vessel in the proportion of about 28 pounds of complex per barrel of oil treated. The temperature was maintained at about 80 F. and the total contact time, during all of which the reaction mixture was stirred, was 4 hours. There was obtained by lili-,ration a gas oil which had a pour point of 30 F.

Example VI A gas oil which had a pour point of 25 F. was contacted in a reaction vessel with an aqueous slurry of urea in the proportion of one volume of slurry to 10 volumes of oil. The aqueous slurry contained 140 pounds of urea per barrel of oil over and above the urea Vrequired to saturate the aqueous solution at about 80 F. There Was no complex recycle in this example. The temperature was maintained at about 80 F. and the reaction vessel total contact time was 18 hours; total stirring time was 4 hours. There was obtained by filtration a gas oil which had a pour point of 10 F.

It will be observed that refrigerator oils of superior quality result from dewaxing lubricating oil stock With aqueous urea in the presence of added complex. The refrigerator oils obtained employing complex recycle in Examples I, II and III are characterized by a Freon haze of between 55 to 65 F. Whereas the refrigerator oil obtained under similar dewaxing conditions without complex recycle in Example IV exhibited substantially no improvement in Freon haze over the charge oil. It is noteworthy that substantially no improvement in Freon haze Was obtained without complex recycle even though the total contact time was 171/2 hours as contrasted With the 1 to 2 hour contact times employed in Examples I, II and III. The substantial improvement in the dewaxing of gas oils obtained employing the process of this invention is also signicant; as a result of dewaxing with an of a gas oil of similar wax content under similar conditions Without complex recycle yielded a gas oil of plus 10 F., which is only a 15 F. improvement.

Although the foregoing examples all illustrate the process of the invention employing an aqueous slurry of urea in the dewaxing of lubricating oil, it is to be understood that the invention Works equally as Well when urea is dispersed in other mediums possessing low hydrocarbon solubility.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made Without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims. Y

We claim:

1. In the formation of urea complexes by contact of a hydrocarbon mixture containing complex-forming constituents with urea in a medium possessing low solubility in said hydrocarbon mixture, the improvement which comprises effecting said contact at a temperature below F. in the presence of a complex consisting of urea and an aliphatic hydrocarbon containing a straight chain of at least six carbon atoms, and being of different composition than the complexforming constituents present in said hydrocarbon mixture, said complex being obtained from a source external to said urea-hydrocarbon mixture.

2. The improvement according to claim 1 in which Water is employed as the urea medium.

3. The improvement according to claim 1 in which a low molecular Weight alcohol is employed as the urea medium.

4. The improvement according to claim l in which a lubricating oil is dewaxed by contact with urea in the presence of a complex comprising urea and normal hydrocarbons of substantially lower molecular Weight than lube oil hydrocarbons.

GEORGE B. ARNOLD. JAMES K. TRUITT. HOWARD V. HESS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,189,128 Breth et al Feb. 6, 1940 2,253,638 McKennon Aug. 26, 1941 2,499,820 Fetterly Mar. 7, 1950 2,549,372 Fetterly Apr. 17, 1951 FOREIGN PATENTS Number Country Date 17,339 Australia Apr. 16, 1948 of 1947 OTHER REFERENCES Bengen, Experientia 5, part 5, page 200 (May 15, 1949).

Zimmershied et al., J. A. C. S., vol. '71, page 2947 (Aug. 1949). 

1. IN THE FORMATION OF UREA COMPLEXES BY CONTACT OF A HYDROCARBON MIXTURE CONTANINING COMPLEX-FORMING CONSTITUENTS WITH UREA IN A MEDIUM POSSESSING LOW SOLUBILITY IN SAID HYDROCARBON MIXTURE, THE IMPROVEMENT WHICH COMPRISES EFFECTING SAID CONTACT AT A TEMPERATURE BELOW 150* F. IN THE PRESENCE OF A COMPLEX CONSISTING OF UREA AND AN ALIPHATIC HYDROCARBON CONTAINING A STRAIGHT CHAIN OF AT LEAST SIX CARBON ATOMS, AND BEING OF DIFFERENT COMPOSITION THAN THE COMPLEXFORMING CONSTITUENTS PRESENT IN SAID HYDROCARBON MIXTURE, SAID COMPLEX BEING OBTAINED FROM A SOURCE EXTERNAL TO SAID UREA-HYDROCARBON MIXTURE. 